T. F. Tout, The Empire and the Papacy, 918-1273
“ The rivalry of Almoravides and Almohades. Yussuf had already died in 1106, but the dissensions of Castile and Leon that followed the death of Alfonso VI. made it easy for his successors to hold their own. Before long, however, the short term of activity of an Oriental dynasty had ended; and the Almoravides saw their African possessions taken away from them by the newer and fiercer power of the Almohades, the Berbers of the Atlas, who had long resented the rule of their brethren of the desert. ”
